A light scanning apparatus, which scans with a light beam, e.g., laser beam irradiated from a light source, is used in optical equipments, e.g., barcode reader, laser printer, head mounted display, or light intake units of imaging apparatuses, e.g., infrared camera.
A conventional light scanning apparatus is disclosed in Japanese Laid-open Patent Publication No. P2006-293116A. The conventional apparatus is shown in FIG. 5. A substrate 52, which is composed of, for example, stainless steel or silicon, is held by a holding member 51 like a cantilever, and an opening part 53 is formed in a free end part of the substrate 52. A mirror section 55 is provided in the opening part 53, and both sides of the mirror section 55 are connected to the substrate 52 by beams 54. A surface of the mirror section 55 is polished like a mirror, reflection coating is formed on the surface of the mirror section 55, or a mirror is adhered thereon.
A vibration source 56, which is composed of a film of a piezoelectric substance, a magnetostrictive substance or a permanent magnet, is provided on the substrate 52. For example, in case of using the piezoelectric substance, the vibration source 56 is extended by applying positive voltage and shrunk by applying negative voltage, so that the substrate 52 is bent. By bending the substrate 52 upward and downward, twisting vibration is generated in the beams 54 and the mirror section 55 is swung.
Driving frequency near resonance frequency of the mirror section 55 and the beams 54 is maintained, and the light scanning operation is performed with reflecting a laser beam by the twisting-vibrated mirror section 55. With this structure, a production cost of the apparatus can be smaller than that of a light scanning apparatus in which a minute mirror produced by a micro electro mechanical system (MEMS) is swung, and great twisting vibration can be generated by a small vibration source.
In the above described light scanning apparatus, characteristics of the apparatus, e.g., scanning angle (amplitude), resonance frequency, will be varied according to manufacturing accuracy of the substrate 52, which is a metal plate, and assembling accuracy of the vibration source. Especially, the scanning angle of the mirror section 55 and the resonance frequency thereof are varied according to a supporting position of the substrate 52, which is held by a base 57 and the holding member 51 like a cantilever (see FIGS. 6A and 6B). Thus, it is desirable to fine-adjust the supporting position of the substrate 52 according to a size of the substrate 52, etc.
In case of attaching the light scanning apparatus to an optical equipment, e.g., laser printer, positional relationship between the mirror section 55 and the base 57 must be maintained in a prescribed tolerance. Positional relationship between a light source, e.g., laser means, of the optical equipment and the light scanning apparatus cannot be varied after attaching the light scanning apparatus. Further, in the light scanning apparatus, positional relationship between the mirror section 55 and the base 57, which supports the mirror section 55 together with the holding member 51, cannot be varied, either. If the positional relationship between the mirror section 55 and the base 57 is varied, the positional relationship between the mirror section 55 and the base 57 cannot maintained in the prescribed tolerance and the laser beam cannot be emitted toward the mirror section 55 as designed.